QALQILIYA, West Bank -- Forces loyal to the moderate Palestinian president stormed a Hamas hideout in the West Bank and set off a gunbattle that left six dead Sunday, the worst violence since the factions fought a pitched battle over Gaza two years ago.
Militants lobbed grenades and fired automatic weapons to push back the raid in a two-story building in Qalqiliya, a West Bank town known for its strong Hamas presence. That drew dozens of President Mahmoud Abbas' forces to the hideout.
When it was over, pools of blood, tear gas canisters and hundreds of spent shell casings littered the floor. Walls were partly burned down during the battle.
Qalqiliya, which elected a Hamas mayor in 2005, was tense Sunday. Women gathered near the scene heaped insults on policemen. Sporadic gunfire erupted in other areas of town, and police said the shots came from Hamas loyalists targeting officers, though there were no reports of injuries.
The two factions have made intermittent attempts to reconcile since Hamas seized Gaza in 2007, leaving rival Fatah in control of only the West Bank. But Sunday's bloodshed showed just how little progress has been made.
The split has complicated Mideast peace efforts because the Palestinians cannot negotiate with Israel in a single voice and Hamas refuses to recognize the Jewish state.
Abbas has backed Washington's peace efforts, and the raid underscored his determination to rein in militants as part of his obligations under the U.S.-backed "road map" peace plan. Last week, Abbas met at the White House with President Obama and renewed a pledge to crack down on militants and honor other commitments under the road map.
The U.S. has been training Abbas' elite forces to help him affirm his control of the West Bank and prepare for eventual statehood. Many of the security personnel involved in the shootout had undergone U.S.-supervised training in Jordan, police said.
Abbas aide Nabil Abu Rdeneh said going after militants is key to one day setting up a Palestinian state.
"To build our country and our state, we need to have one authority, one gun, one law," he said.
Since Hamas' Gaza takeover, Abbas' security forces have detained hundreds of Hamas supporters in the West Bank and closed the group's institutions and charities.
Among those killed in the raid were two top Hamas militants who had been on the run from Israel for years. An unarmed Hamas supporter and three Palestinian policemen linked to Abbas' forces also died.
Tens of thousands of backers of Hamas and other militant groups marched in several places in Gaza City, protesting the raid and calling Abbas a "collaborator" with Israel. Abu Obeida, a spokesman for the Hamas military wing, threatened "tough and harsh reprisal."
The Qalqiliya clash began late Saturday when Palestinian troops surrounded a hideout of Mohammed Samman, a leader of Hamas' military wing, and his assistant, Mohammed Yassin. Both had been on Israel's wanted list for six years, Palestinian security officials said.
Initially, about two dozen officers stormed the house, breaking down the door, said a policeman who participated in the raid. He spoke on condition of anonymity because he was not authorized to speak to reporters. The Hamas men lobbed a grenade and opened automatic fire, killing three officers and wounding two critically, he said. Other officers fled, then brought in reinforcements.
The ensuing battle lasted until midmorning Sunday. Police say they found bombs, suicide belts and bullets in their search of the house.
Security officials seized the bodies of the Hamas militants, fearing a public burial would turn into angry protests against the Palestinian Authority. Muslim tradition demands the dead should be buried quickly.
Hamas officials in the West Bank said that some 40 loyalists of the group had been arrested in Qalqiliya in the past week as part of the search for the top two fugitives. Some 200 Hamas supporters are in Palestinian Authority custody.
Associated Press writers Diaa Hadid and Dalia Nammari in Ramallah, West Bank, Ibrahim Barzak in Gaza City and Matti Friedman in Jerusalem contributed to this report.